Active matrix type liquid crystal display system and driving method therefor

ABSTRACT

An active matrix type liquid crystal display system having a plurality of switching elements to which scanning signals and image signals are applied via scanning electrodes and signal electrodes on one of a pair of the substrates and a liquid crystal layer interposed between the pair of substrates, and an electrode structure for generating an electric field having a component substantially in parallel with one of the pair of the substrates. Scanning signals having at least two kinds of non-selective voltage values are applied to the scanning electrodes, whereby power consumption is reduced and image degradation of cross talk of the display system is prevented, in addition to obtaining extremely wide viewing-angle characteristics.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an active matrix type liquid crystaldisplay system such as a display unit used in a personal computer and adriving method therefor.

2. Description of the Prior Art

At present, active matrix type (thin film transistor type) liquidcrystal display systems are widely used in a great variety of use, andrequired to be improved in multi-level half-tone (full color).

As a display type for liquid crystal display system, there is so-calledtwisted nematic display type (thereinafter referred to as "verticalelectric field type") wherein liquid crystal is filled between twosubstrates facing to each other having a flat display electrode on eachof the facing surfaces of the substrates, electric field nearly normalto the substrate surface being applied to the liquid crystal to drive.The liquid crystal display system of this type has been already in themarket.

On the other hand, another new different type has been proposed, forexample, in Japanese Patent Publication No. 63-21907 (1988), wherein apair of electrodes for applying electric field to liquid crystal areformed on an identical substrate, liquid crystal being driven byapplying the electric field to the liquid crystal in the directionapproximately parallel to the surfaces of substrate (thereinafterreferred to as "parallel electric field type").

In order to produce multi-level halftone display in a thin transistortype liquid crystal display system, the voltage output from the circuitfor supplying image signal to signal electrodes, that is, a signaldriver IC, needs to have a multi-level output value corresponding to thenumber of the multi-level halftone. In a case of producing, for example,16 levels of halftone, the signal driver IC needs to be capable ofsupplying 16×2 (binary values of positive and negative are required foreach halftone, since liquid crystal needs to be driven with alternatingcurrent.) =32 values of output voltages. Since the signal driver IC hasoperation amplifiers in the output stages each in order to be capable ofsupplying sufficient current, it is necessary to provide 32 operationamplifiers in the above case. The smaller the operation amplifier in theoutput stage can be made and consequently the smaller the signal driverIC can be made, the lower the absolute maximum supply is. Although theproductivity of the signal driver IC may be improved and the size of theouter frame portion of the display system may be made small by means ofdeceasing the size of the signal driver IC, the maximum output voltagefor the signal voltage needs to be decreased.

On the other hand, in the parallel electric field type the voltage isapplied to the liquid crystal layer with a pair of non-transparentline-shaped electrodes formed on an identical substrate although in thevertical electric field type described above the voltage is applied tothe liquid crystal layer with a pair of transparent flat-shapedelectrodes facing to each other. Consequently, in the parallel electricfield type the opening ratio becomes small. In this reason, since thedistance between the two electrodes cannot be so small, the distancebetween the two electrodes is larger than and the magnitude of electricfield in the parallel electric field type is weaker than those in thevertical electric field type. In order to produce the same magnitude ofthe strength of electric field, therefore, the former needs to applyhigher voltage between the electrodes than the latter.

An object of the present invention is to provide an active matrix typeliquid crystal display system of parallel electric field type and adriving method thereof in which the display system is operable with apractically sufficiently low drive voltage of signal side drive circuit.Another object of the present invention is to provide an active matrixtype liquid crystal display system of parallel electric field type and adriving method thereof in which cross-talk, especially, lateral smeardoes not appear and high image quality can be attained.

SUMMARY OF THE INVENTION

In order to attain the above objects, according to the presentinvention, the structure of an active matrix type liquid crystal displaysystem is as follows.

(1) An active matrix type liquid crystal display system, wherein aliquid crystal composition is interposed between a first and a secondsubstrates, a plurality of pixel parts being constructed with aplurality of scanning electrodes and a plurality of signal electrodesarranged in a matrix, switching element being provided in each of thepixel parts where a switching element is formed.

the pixel electrode and a counter electrode connected to the switchingelement are placed such a way that the electric field is applied inparallel to the substrate, the liquid crystal in the liquid crystalcomposition layer being driven with the voltage applied between theelectrodes in keeping the major axes of the liquid crystal moleculesparallel to the surface of the substrate, the system having the elementstructure capable of obtaining a light state of the liquid crystalcomposition and a dark state with orientation state and the polarizemeans, having drive means capable of putting out a scanning signalhaving more than two non-selective voltage in the scanning electrode.

(2) According to another feature of the present invention, an activematrix type liquid crystal display system, wherein the counter electrodeis a common electrode provided separately from the scanning electrode,the signal electrode, the pixel electrode.

(3) According to a further feature of the present invention, an activematrix type liquid crystal display system, wherein the counter electrodeis a part of the scanning electrode adjacent to the pixel part.

(4) According to a further feature of the present invention, an activematrix type liquid crystal display system, wherein the relation betweenthe threshold value V_(TH) for the switching transistor element and themaximum voltage V_(ON) between the pixel electrode and the counterelectrode for obtaining light state or dark state satisfies thefollowing equation.

    V.sub.TH >|V.sub.ON |

(5) According to a further feature of the present invention, an activematrix type liquid crystal display system, wherein the relation amongthe threshold value V_(TH) for the switching transistor element, themaximum voltage V_(ON) between the pixel electrode and the counterelectrode for obtaining light state or dark state and the minimumvoltage VO_(OFF) between the pixel electrode and the counter electrodefor obtaining light state or dark state satisfies the followingequation.

    V.sub.TH >(|V.sub.ON |-|V.sub.OFF |)/2

(6) According to a further feature of the present invention, an activematrix type liquid crystal display system, wherein the switchingtransistor elements are constructed so aligned as to have p-type andn-type characteristic in alternate order by every row.

(7) According to a further feature of the present invention, an activematrix type liquid crystal display system, wherein at least two of theswitching transistor elements are formed in a pixel, at least one of thesource electrode or the drain electrode of the thin film transistorelement being connected to the signal electrode, at least one of thesource electrode or the drain electrode of the thin film transistorelement being electrically connected to the scanning electrode in theimmediately following row.

(8) According to a further feature of the present invention, an activematrix type liquid crystal display system, wherein at least two of theswitching transistor elements are formed in a pixel, at least one of thesource electrode or the drain electrode of the thin film transistorelement being connected to the signal electrode, at least one of thesource electrode or the drain electrode of the thin film transistorelement being connected to the scanning electrode in the immediatelyfollowing row through a capacitive element.

(9) According to a further feature of the present invention, an activematrix type liquid crystal display system, wherein the liquid crystalcomposition, the direction of rubbing, the configuration of thepolarization plate, the distances between the substrates, and thedistance between the pixel electrode and the counter electrode are setsuch that the difference between the voltage for obtaining light stateand the voltage for obtaining dark state becomes below 5 V.

(10) According to a further feature of the present invention, an activematrix type liquid crystal display system, wherein the scanning signaloutputs at least two kinds of the non-selective voltage values.

(11) According to a further feature of the present invention, an activematrix type liquid crystal display system, wherein the voltage in thepixel electrode is changed by means of changing the non-selectivevoltage for the scanning signal applied to the scanning electrode mainlythrough the capacitance between the scanning electrode and the pixelelectrode.

(12) According to a further feature of the present invention, an activematrix type liquid crystal display system, wherein the non-selectivevoltages of the scanning signals applied to the scanning electrodes inall of the rows are changed with the identical amplitude, the identicalcycle and the identical phase.

(13) According to a further feature of the present invention, an activematrix type liquid crystal display system, wherein scanning signal,which has binary values of the non-selective voltages in alternate orderby every frame and being kept at a constant voltage during non-selectiveperiod, is applied to the scanning electrode, the signal electrodereceiving the image signal transmitted in such a way that the polarityof the voltage between the pixel electrode and the counter electrodediffers in alternate order by every row.

(14) According to a further feature of the present invention, an activematrix type liquid crystal display system, wherein the voltagedifference between the two kinds of non-selective voltage values is setequal to the sum of the maximum voltage V_(ON) between the pixelelectrode and the counter electrode for obtaining light state or darkstate and the minimum voltage V_(OFF) between the pixel electrode andthe counter electrode for obtaining light state or dark state.

(15) According to a further feature of the present invention, an activematrix type liquid crystal display system, wherein the voltagedifference between the two kinds of non-selective voltage values is setequal to the half of the sum of the maximum voltage V_(ON) between thepixel electrode and the counter electrode for obtaining light state ordark state and the minimum voltage V_(OFF) between the pixel electrodeand the counter electrode for obtaining light state or dark state.

(16) According to a further feature of the present invention, an activematrix type liquid crystal display system, wherein the central voltageof the non-selective voltage in the scanning signal applied to thescanning electrode having p-type switching transistor element is higherthan the central voltage of the non-selective voltage in the scanningsignal applied to the scanning electrode having n-type switchingtransistor element, the voltage difference exceeding the maximum voltageV_(ON) between the pixel electrode and the counter electrode forobtaining light state and dark state.

(17) According to a further feature of the present invention, an activematrix type liquid crystal display system, wherein the counter electrodevoltage is supplied from the scanning electrode.

(18) According to a further feature of the present invention, an activematrix type liquid crystal display system, wherein the counter electrodevoltage supplied from the scanning electrode changes according to thepolarity of the image signal voltage.

The operations of the present invention will be described below.

The following operations of the present invention are produced bychanging the non-selective voltage (OFF voltage) in the scanning signalsupplied to the scanning electrode during non-selective period, andemploying the parallel electric field type as the drive type forchanging the voltage in the pixel electrode through the capacitivecoupling between the pixel electrode and the scanning electrode, whichhas been discovered by the inventors of the present invention.

(First operation)

In parallel electric field type, the capacity C_(LC) between the pixelelectrode and the common electrode is smaller than that in verticalelectric field type, because in the vertical electric field type thepixel electrode and the counter electrode forms a parallel planecapacitance. Therefore, in the parallel electric field type, thecapacitance C_(S) between the pixel electrode and the scanning electrodeis relatively larger than the capacitance C_(LC) between the pixelelectrode and the counter electrode, and consequently a sufficient biasvoltage can be applied to the pixel electrode depending on voltagechange in the scanning electrode. Thereby, the ratio of the areaoccupied by the capacitance element C_(S) formed between the pixelelectrode and the scanning electrode to the area of the one pixelelement can be decreased, which improves the opening ratio.

(Second operation)

Since the capacity C_(LC) between the pixel electrode and the counterelectrode is small, the load capacity of the scanning electrode becomessmall. Therewith, a driving method applying a modulation voltage to thescanning electrode has an advantage in that the distortion in themodulation wave form is small. Thereby, the ratio of the load capacityin the scanning electrode changed depending on image is decreased, andthe ratio of the wave form deformation in the non-selective voltage forthe scanning signal is also decreased. Therefore, the modulating voltagecan be applied uniformly, occurrence of cross-talk (horizontal smear inwhich horizontally drawn lines appear) can be suppressed.

(Third operation)

In the parallel electric field type, the adjacent scanning electrode canbe used as a counter electrode. Therewith, the area to be used by trunkpart of the counter electrode may be used for the opening part toincrease the opening ratio. Further, the number of cross points in theinterconnecting electrode is decreased, which decreases short circuitfailure in the electrodes.

In order to drive the liquid crystal with alternating current, imagesignal is charged into the signal electrode in such a manner that thevoltage wave form charged in the pixel electrode against the counterelectrode becomes an alternating wave form. However, the typical activeelement used in the active matrix type liquid display system, such asamorphous silicon thin film transistor (a-SiTFT), poly-silicon thin filmtransistor (p-SiTFT) and so on, has a characteristic where drain currentinitiates to flow at the scanning voltage of approximately 0 V, that is,the threshold voltage V_(TH) is approximately 0 V. Therefore when thenon-selective voltage for the scanning voltage (OFF level) is used asthe counter electrode voltage, the transistor element described abovecannot keep negative voltage against the counter electrode voltage evenif it is charged. The reason is that since the OFF level of the scanningvoltage is in a higher level than the voltage of the pixel electrode,the transistor element having the threshold voltage V_(TH) ofapproximately 0 V enters into ON state, the voltage of the pixelelectrode decreases up to the OFF level for the scanning voltage throughleakage. Therefore, in order to drive the liquid crystal withalternating current, it is required to provide a counter electrodeseparately to set the counter electrode voltage higher than the OFFlevel of the scanning voltage. By means of employing a transistor havinga high threshold voltage, it becomes possible to drive the liquidcrystal with alternating current since the pixel electrode can becharged and kept in a negative voltage against the counter voltage evenwhen the scanning electrode is used as a counter electrode and the OFFlevel of the scanning voltage being used as a counter electrode voltage.The present invention is characterized that the threshold value V_(TH)for the switching transistor element exceeds the maximum voltage V_(ON)applied to the liquid crystal or the half of the difference between themaximum voltage V_(ON) and the minimum voltage V_(OFF). Therewith, evenif a negative voltage is applied to the liquid crystal, the pixelelectrode voltage does not leak but is kept, the liquid crystal beingdriven with alternating current and with low voltage.

Further, the transistor elements are constructed such as to have p-typeor n-type characteristic every other row, the central voltage of thenon-selective voltage in the scanning signal applied to the scanningelectrode having p-type switching transistor element being higher thanthe central voltage of the non-selective voltage in the scanning signalapplied to the scanning electrode having n-type switching transistorelement, the voltage difference exceeding the maximum voltage V_(ON)between the pixel electrode and the counter electrode for obtaininglight state or dark state. Therewith, even if the threshold voltageV_(TH) is near 0 V or lower than 0 V, the liquid crystal can be drivenwith alternating current and with low voltage.

Furthermore, two thin film transistor elements are constructed in apixel, image signal voltage being supplied from one of the thin filmtransistor element, counter electrode voltage being supplied from theother thin film transistor element. Therewith, the liquid crystal can bedriven with alternating current. Further, by means of changing thecounter electrode voltage corresponding to the polarity of image signalvoltage, the liquid crystal can be driven with low voltage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of Embodiment 1 of a liquid crystaldisplay system in accordance with the present invention, taken along theline 1--1 in FIG. 3.

FIG. 2 is a front view showing the structure of a pixel in Embodiment 1including the adjacent pixels.

FIG. 3 is a front view showing the structure of a pixel in Embodiment 1in accordance with the present invention.

FIG. 4 is a cross-sectional side view taken along the line 4--4 in FIG.3.

FIG. 5 is a cross-sectional side view taken along the line 5--5 in FIG.3.

FIG. 6 is a view showing the construction of a display system inEmbodiment 1 in accordance with the present invention.

FIG. 7 is a chart showing the drive wave form in Embodiment 1 inaccordance with the present invention.

FIG. 8 is a chart showing the drive wave form in Embodiment 2 inaccordance with the present invention.

FIG. 9 is a front view showing the structure of a pixel in Embodiment 3including the adjacent pixels.

FIG. 10 is a front view showing the structure of a pixel in Embodiment 3in accordance with the present invention.

FIG. 11 is a cross-sectional side view being taken along the line 11--11in FIG. 10.

FIG. 12 is a view showing the construction of a display system inEmbodiment 3 in accordance with the present invention.

FIG. 13 is a chart showing the drive wave form in Embodiment 3 inaccordance with the present invention.

FIG. 14 is a front view showing the structure of a pixel in Embodiment 4including the adjacent pixels.

FIG. 15 is a front view showing the structure of a pixel in Embodiment 4in accordance with the present invention.

FIG. 16 is a view showing the construction of a display system inEmbodiment 4 in accordance with the present invention.

FIG. 17 is a chart showing the drive wave form in Embodiment 4 inaccordance with the present invention.

FIG. 18 is a chart showing the drive wave form in Embodiment 5 inaccordance with the present invention.

FIG. 19 is a chart showing the drive wave form in Embodiment 6 inaccordance with the present invention.

FIG. 20 is a chart showing the drive wave form in Embodiment 7 inaccordance with the present invention.

FIG. 21 is a front view showing the structure of a pixel in Embodiment 8in accordance with the present invention.

FIG. 22 is a view showing a passing through circuit of a pixel inEmbodiment 8.

FIG. 23 is a cross-sectional side view taken along the line E-E' in FIG.21.

FIG. 24 is a cross-sectional side view taken along the line F-F' in FIG.21.

FIG. 25 is a cross-sectional side view taken along the line G-G' in FIG.21.

FIG. 26 is a view showing the construction of a display system inEmbodiment 8 in accordance with the present invention.

FIG. 27 is a chart showing the drive wave form in Embodiment 8 inaccordance with the present invention.

FIG. 28 is a front view showing the structure of a pixel in Embodiment 9in accordance with the present invention.

FIG. 29 is a view showing a passing through circuit of a pixel inEmbodiment 9.

FIG. 30 is a chart showing the drive wave form in Embodiment 10 inaccordance with the present invention.

FIG. 31 is a view showing the operation of the liquid crystal in aliquid crystal display system in accordance with the present invention.

FIG. 32 is a view showing the angle of the direction of the orientationof molecular main axis (rubbing direction) φ_(LC) and the angle of thedirection of polarization axis of the polarization plate φ_(P) on theinterface against the direction of electric field.

FIG. 33 is a graph showing the photo-electric characteristic inEmbodiment in accordance with the present invention, being takennormally closed type as an example.

FIG. 34 is a view showing the dependence of photoelectric characteristicon the direction of the orientation of molecular main axis (rubbingdirection) φ_(LC) on the interface, being taken normally closed type asan example.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Embodiment 1!

FIG. 1 shows the cross-sectional structure of one pixel region in aliquid crystal display panel. The liquid crystal panel comprises anupper substrate, a lower substrate and a liquid crystal layer filledbetween the gap between the both. By applying voltage between a pixelelectrode 3 and a counter electrode 4 formed on the lower substrate, theelectric field produced between both of the electrodes is controlled tocontrol the orientation state of the liquid crystal and change thetransmitting ratio of light from a back light passing through the panel.When seeing from the opposite side of the back light in the liquidcrystal panel, light state, dark state or middle state of the both isobserved by means of controlling the voltage applied between the pixelelectrode and the counter electrode. The pixel electrode and the counterelectrode are extended in line-shape in the direction normal to thepaper surface of FIG. 1, the distance between the both electrodes isapproximately 15 μm. Since the thickness of the liquid crystal layer isapproximately 4 μm and is smaller than the gap of 15 μm between thepixel electrode and the counter electrode, the direction of the electricfield 101 (line of electric force) produced inside the liquid crystallayer becomes nearly the lateral direction of FIG. 1 (FIG. 1 is a figureexpanded in the thickness direction of the display panel comparing tothe actual system).

FIG. 31 schematically shows the orientation states of the liquid crystalmolecules in the cases of applying and not applying voltage between thepixel electrode 3 and the counter electrode 4. FIG. 31 (a) and (b) areviews seeing the liquid crystal panel from the lateral direction, FIG.31 (c) and (d) being views seeing from the top and the bottom. And FIG.31 (a) and (c) are views when voltage is not applied, FIG. 31 (b) and(d) being views when voltage is applied. By applying different voltagesto the pixel electrode and the counter electrode respectively to produceelectric potential difference between the both and to apply electricfield to the liquid crystal composition layer, the liquid crystalmolecules react with the mutual reaction of the dielectric anisotropy ofthe liquid crystal composition and the electric field to change theorientation to the direction of the electric field. As shown in FIG. 1and FIG. 31, polarization plates 8 are formed on the upper and the lowersurfaces of the liquid crystal panel, and the transmitting ratio oflight passing through the liquid crystal panel is changed by the mutualreaction of the anisotropy in refraction coefficient of the liquidcrystal composition layer and the polarization plates. Therewith, thebrightness in the display is changed.

By FIG. 32, the angle of the direction 102 of the main axis of theliquid crystal molecule (optical axis) φ_(LC) near the interface and theangle of the direction 103 of polarization axis of the polarizationplate φ_(P) against the direction of electric field 101 are defined.Since there are pairs of the polarization plate and liquid crystalinterface in the top and in the bottom respectively, these angles areindicated by φ_(P1), φ_(P2), φ_(LC1), φ_(LC2) according to necessity.During lack of electric field, the liquid crystal molecules of rod-shape5 are orientated in such a direction as to have a little angle againstthe longitudinal direction of the pixel electrode 3 and the counterelectrode 4 (refer to the front view of FIG. 31 (c)), that is, 45degrees ≦|φ_(LC) |<90 degrees. In FIG. 31 and FIG. 32, the direction ofthe main axis orientation (rubbing) 103 of the liquid crystal moleculeson the interface is denoted by an arrow. It is a preferable conditionfor the direction of the main axis orientation of the liquid crystalmolecules on the top and the bottom interfaces to be parallel to eachother, that is, φ_(LC1) =φ_(LC2) (=φ_(LC)). It is supposed here that thedielectric anisotropy of the liquid crystal composition is positive.

FIG. 33 shows characteristic in the relation between the brightness andthe voltage V_(LC), being applied between the pixel electrode and thecounter electrode, that is, so-called the photo-electric characteristic.The brightness in the ordinate is indicated by relative value when themaximum value for the brightness is set as 100%. As the applied voltageincreases, the brightness sharply increases at the voltage V_(OFF), andthen the brightness monotonously increases up to near the voltage V_(ON)as the applied voltage increases.

As shown in FIG. 1, further formed on the upper substrate are a colorfilter 11 for color display, a shielding film (black matrix) 23 forimproving contrast by means of shielding the light passing through thenon-control region against the light around a pixel (the region wherethe light transmitting ratio cannot be controlled by the voltage appliedbetween the pixel electrode and the counter electrode), a flatteningfilm 12 for flattening the surface of the substrate, and an orientationcontrol film 6 for controlling the orientation of the liquid crystalmolecules such as to orientate in a given direction when the voltage isnot applied. These films are formed on a transparent substrate 7 such asglass, plastic resin and so on.

On the lower substrate, various kinds of interconnection a thin filmtransistor (TFT) for switching the voltage applied to the pixelelectrode and so on are formed other than the pixel electrode or thecounter electrode, which will be described later. These are formed on atransparent substrate 7 such as glass and so on similar to in the caseof the upper substrate. In the embodiment, transparent glass substratespolished on their surfaces having thickness of, for example, 1.1 mm areused as the substrates 7. On one of the substrate, a thin filmtransistor is formed, and further an orientation film 6 is formed on theuppermost surface. In the embodiment, polyimide is employed as theorientation film 6, its surface being treated with rubbing fororientating the liquid crystal 5. On the other substrate, polyimide isalso applied and treated with rubbing. The direction of rubbing on bothof the upper and the bottom interfaces are nearly parallel to eachother, and the angle of the rubbing against the direction of electricfield is 88 degrees (φ_(LC1) =φ_(LC2) =88°). A nematic liquid crystalcomposition having dielectric anisotropy Δε of positive and 4.5, ananisotropy of refractive index Δn of 0.072 (589 nm, 20° C.) isinterposed between the substrates. The gap d is 3.9 μm under filling ofthe liquid crystal and kept by means of dispersing and interposingspherical polymer beads. Therefore, Δn·d becomes 0.281 μm. The panel issandwiched with two polarization plates 8 G1220DU, a product of NittoDenkou Co.!, the polarization transmitting axis in one of thepolarization plates being set in such as to have a little angle againstthe direction of rubbing, that is, φ_(P1) =80° (therefore, |φ_(LC1)-φ_(P1) |=8°), and the polarization transmitting axis in the other ofthe polarization plates being set in such as to intersect with theformer in right angle, that is, φ_(P2) =-10°. Therewith, it has beenrealized the characteristic where as the voltage V_(LC) applied to thepixel according to the present invention (the voltage between the pixelelectrode 3 and the counter electrode 4) increases from zero, thebrightness decreases up to a minimum value (FIG. 33). The embodimentemploys the normally closed characteristic where dark state is obtainedat a low voltage (V_(OFF) ) and light state at a high voltage (V_(ON)).Therein, V_(OFF) is 6.9 V and V_(ON) is 9.1 V. Although the normallyclosed characteristic is employed in the embodiment, the normally openedcharacteristic may be employed. Further, the liquid crystal havingnegative dielectric anisotropy may be used.

FIG. 2 shows the plan configuration of various kinds of electrodes,interconnections and TFT's formed on the liquid crystal layer side ofthe lower substrate. The numeral 1 indicates scanning electrodes (gateelectrodes) which extend in the lateral direction in the figure and areformed in plural number in parallel to each other. The numeral 2indicates signal electrodes (drain electrodes) which extend in thevertical direction in the figure intersecting with the scanningelectrodes and are formed in plural number in parallel to each other.Pairs of signal electrodes composed of the two adjacent signalelectrodes are formed in plural number. A counter electrode 4 is formedbetween a pair of signal electrodes and the adjacent pair of signalelectrodes. Each of the counter electrodes is composed of a trunk partextending in the vertical direction in the figure, and branch partsextending from the trunk part and bending toward right and left sides.As shown in the figure, one pixel is the region surrounded by a signalelectrode 2, trunk part of a counter electrode 4 adjacent to the signalelectrode, and two scanning electrodes adjacent to each other. A TFT 15is formed on the scanning electrode in each of the pixels. The numeral 3indicates a pixel electrode (source electrode) which extends in bendingin an inverted U-shape from each of the TFT's. A part of the pixelelectrode overlaps with the adjacent scanning electrode, and on the parta storage capacitance element 16 being formed.

In the embodiment, the pixel pitch is 110 μm in the direction of thescanning electrode, and 330 μm in the direction of the signal electrode.Concerning the width of electrodes, for the scanning electrode 1, of thesignal electrode 2, of the trunk of the counter electrode 4 which areformed along plural pixels, a wide width of 10 μm is employed to avoidfailure owing to breaking.

On the other hand, in order to improve opening ratio, for the pixelelectrode 3 and the branch part extending from the trunk of the counterelectrode 4, a narrow width of 6 μm is employed. In addition to this,number of the counter electrode inyrtvonnrvyiond is decreased by a halfby means of forming one counter electrode for two lateral alignments ofpixels. Therewith, the opening part can be further expanded, and theprobability of circuit short (proportional to the intersecting area ofelectrodes) in the intersecting part of the counter electrode 4 and thescanning electrode 1 is decreased. In the embodiment, the number of thesignal electrodes is set in 640×3, the number of the scanning electrodesbeing set in 480, the number of the counter electrodes being set in 960.Then the number of the pixels becomes approximately one million.

FIG. 3 is an enlarged view showing the part of one pixel in FIG. 2. FIG.1 described above is a cross-sectional view being taken on the plane ofthe line 1--1 in FIG. 3. FIG. 4 and FIG. 5 are cross-sectional viewsbeing taken on the planes of the lines 4--4 and 5--5 in FIG. 3respectively.

As shown in FIG. 4, the TFT has an inverted stagger structure, a gateinsulator 9 (for example, silicon nitride) being formed on the scanningelectrode 1, an amorphous silicon layer 22 being formed thereon.Further, a drain electrode 2 and a source electrode 3 are formed withconnecting to the amorphous silicon layer. The drain electrode and thesource electrode in the TFT are constructed with a part of the signalelectrode and the pixel electrode respectively. Between the drain andthe source electrodes and the amorphous silicon layer 22, an n+-typeamorphous silicon layer is formed as an ohmic contact layer which is notshown in the figure. In the embodiment, the signal electrode 2, thepixel electrode 3 and the counter electrode 4 are made of the samemetallic material (for example, aluminum).

As shown in FIG. 5, a gate insulator 9 is interposed between thescanning electrode 13 and the pixel electrode 3 to form a storagecapacitance capacity element 16. The area of the storage capacitance inthe embodiment is extremely smaller than that in a case of aconventional vertical electric field type, the capacitance is a smallvalue of C_(S) =200 fF.

Although the storage capacitance in the embodiment is formed with thescanning electrode in the precedent row and the pixel electrode, thestorage capacitance may be formed with the scanning electrode in thefollowing row and the pixel electrode. And although the trunk portion ofthe counter electrode is commonly utilized with the two adjacent lateralalignments of pixels, it does not essentially change the effect of thepresent invention and is in the scope of the present invention if onetrunk of the counter electrode is formed for each of the lateralalignment of the pixels.

Circuit diagram and driving waveform will be described below.

FIG. 6 shows the circuit diagram of a liquid crystal display system inaccordance with the present invention. The numeral 21 indicates adisplay region, a plurality of scanning electrodes 1 are formed in thelateral direction and a plurality of signal electrodes 2 and counterelectrodes are formed in the vertical direction, a TFT is formed in eachof the intersecting parts of the scanning electrode and the signalelectrode. The gate electrode G of the TFT is connected to the scanningelectrode, and the drain electrode is connected to the signal electrode.A liquid crystal capacitance C_(LC) is formed between the sourceelectrode S of the TFT and the counter electrode 4, a storagecapacitance C_(S) being formed between the source electrode S and thescanning electrode. The pixel electrode 3, the counter electrode 4 andthe liquid crystal layer shown in FIG. 1 electrically form a capacitanceC_(LC). The storage capacitance C_(S) is an absolutely essentialcapacitance for suppressing the feedthrough voltage entering into thevoltage in the pixel electrode 3 through the capacitance C_(GS) betweenthe gate electrode and the source electrode of the TFT when the scanningsignal voltage in the scanning electrode 1 is transferred from theselective voltage to the non-selective voltage, and is required to havea sufficiently large capacitance comparing to C_(GS) (for example,approximately 10 times as large as C_(GS)).

The numeral 18 in FIG. 6 indicates a scanning driver which applies thescanning voltage for control the conduction state (ON) and thenon-conduction state (OFF) of the TFT and the modulation voltage, whichwill be described later, to the scanning electrodes from the top to thebottom in the figure consecutively (the line-at a-time method). Thenumeral 19 indicates a signal driver which supplies the image signal tobe displayed to each of the signal electrodes. When the aselective-voltage (ON voltage) for TFT is applied to a scanningelectrode, the TFT connected to the scanning electrode is brought intoconduction state, the image signal supplied to the signal electrode isapplied to the pixel electrode composing the liquid crystal capacitanceC_(LC) through the TFT. The numeral 17 indicates a control circuit forcontrolling operation of the scanning driver 18 and the signal driver19, and the numeral 20 indicates a counter electrode drive circuit forsupplying voltage to counter electrodes.

The present invention is characterized by employing a driver LSI capableof putting out at least three kinds of values to the scanning driver 18,or characterized by the scanning driver 18 capable of putting out atleast three kinds of voltage values.

In the other hand, the signal driver 19 has the circuit capable ofapplying the voltage waveform having image information to the signalelectrode 2, and is constructed such that the maximum amplitude V_(DP-P)(V_(DH) -V_(DL) in FIG. 7) in the signal voltage waveform becomes ΔV(refer to FIG. 33: ΔV=V_(ON) -V_(OFF)). In the embodiment, a constantvoltage is applied to the counter electrode.

FIG. 7 shows driving waveforms output from the drive circuit in theembodiment. FIG. 7 (a) shows the scanning signal waveform V_(G)(i-1)applied to the (i-1)-th scanning electrode by the scanning driver 18,FIG. 7 (b) showing the scanning signal waveform V_(G)(i) applied to thei-th scanning electrode by the scanning driver 18, FIG. 7 (c) showingthe signal waveform V_(D)(j) applied to the j-th signal electrode by thesignal driver 19, FIG. 7 (d) showing the voltage waveform V_(C) appliedto the counter electrode. FIG. 7 (e) shows the voltage V_(S) applied tothe pixel electrode 3 of the pixel formed in the intersecting part ofthe i-th scanning electrode and the j-th signal electrode when the abovevoltages are applied to the scanning electrode, the signal electrode andthe counter electrode. The signal waveform having image information isapplied to the signal electrode 2, and the scanning signal waveform isapplied to the scanning electrode 1 in synchronizing with the imagesignal waveform. The image signal voltage is transmitted to the pixelelectrode 3 from the signal electrode 2 through the TFT 15, the voltagebeing applied to the liquid crystal part between the pixel electrode andthe counter electrode 4. Therein, the non-selective voltage (OFFvoltage) for the scanning signal waveform V_(G) supplied to the scanningelectrode 1 is modulated, the voltage in the pixel electrode 3 beingchanged by the capacitive coupling when the TFT 15 is in OFF-state, thebias voltages V_(B)(+) and V_(B)(-) are applied to the voltage in thepixel electrode 4. Therein, V_(B)(+) shows the bias voltage for evennumber frames (positive frames) and V_(B)(-) shows the bias voltage forodd number frames (negative frames). Therewith, the voltage of thevoltage V_(S) in the pixel electrode 3 subtracting the voltage V_(C) inthe counter electrode 4, that is, the voltage applied to the liquidcrystal V_(LC) =V_(S) -V_(C), is substantially increased comparing tothe case where the OFF-voltage in the waveform V_(G) supplied to thescanning electrode is not modulated (constant voltage). The amplitudesof the bias voltage V_(B)(+) and V_(B)(-) applied to the pixel electrode3 for the variation ΔV_(GL) (ΔV_(GL)(+) =V_(GL) -V_(GLL) or ΔV_(GL)(-)=V_(GLH) -V_(GL)) is expressed as follows.

    V.sub.B =(C.sub.S /C.sub.T)ΔV.sub.GL                 (1)

where C_(S) is the capacitance of the storage capacitance element 16,C_(T) is the total capacitance (C_(S) +C_(LC) +C_(GS) +C_(DS)).Therefore, by means of setting the amplitude of the bias voltage V_(B)for the normally closed in

    V.sub.B =V.sub.OFF +ΔV/2,                            (2)

and for the normally open in

    V.sub.B =V.sub.ON +ΔV/2,                             (3)

the voltage ΔV/2 is supplied to the center voltage of drain voltageV_(D-CENTER) into the signal electrode 2 from the signal driver 19 whenlight state is obtained (in a case of even frame), and -ΔV/2 when darkstate is obtained (in a case of even frame). The maximum amplitudeV_(DP-P) (=V_(DH) -V_(DL)) is decreased up to ΔV (FIG. 33). (In a caseof odd frame, the voltage -ΔV/2 is supplied to the center voltage whenlight state is obtained, and ΔV/2 when dark state is obtained. Thevoltage for obtaining a middle halftone is in the same way as above.)

In the liquid crystal display element of the parallel electric fieldtype in the embodiment, since a wire-shaped pixel electrode 3 and awire-shaped counter electrode 4 are placed on an identical substrate inparallel to each other, the liquid crystal capacitance C_(LC) is 33 fF,and is approximately one-tenth as small as that of approximately 370 fFin the conventional vertical electric field type where the liquidcrystal capacitance is formed by facing the flat-shaped pixel electrodeand the flat-shaped counter electrode to each other. Therefore, in acase where the driving method supplying the bias voltage into the pixelelectrode from the scanning electrode is employed in the parallelelectric field type, when the parasitic capacitance in the TFT(especially, the capacitance between the gate electrode and the sourceelectrode C_(GS)) is set sufficiently small comparing to C_(S), C_(T)≈C_(S). From Equation 1, the change in the non-selective voltage ΔV_(GL)itself becomes the bias voltage V_(B), a sufficient bias voltage can beapplied. In the embodiment, the preset values for the voltage waveformsin FIG. 7 are as follows; V_(D-CENTER) =23.0 V, V_(GH) =28.6 V, V_(GL)=0, V_(DH) =24.5 V, V_(DL) =21.6 V, V_(GLH) =9.0 V, V_(GLL) =-9.0 V,V_(C) =22.3 V. As the result, the voltage shift due to the parasiticcapacitance C_(GS) between the gate electrode and the source electrodeΔV_(GS)(+), ΔV_(GS)(-), ΔV_(B), the bias voltage V_(B), theroot-mean-square value V_(rms) of the voltage V_(LC) applying to liquidcrystal are as shown in Table 1.

                  TABLE 1                                                         ______________________________________                                        Various Kinds of Voltage Values                                               Display                                                                       state            Light  Dark                                                  ______________________________________                                        ΔV.sub.GS(+)                                                                             0.44   0.59                                                  ΔV.sub.GS(-)                                                                             0.82   0.78                                                  V.sub.B(+)       7.61   8.31                                                  V.sub.B(-)       7.61   8.31                                                  ΔV.sub.B(-)                                                                              0.14   0.15                                                  ΔV.sub.B(+)                                                                              0.14   0.15                                                  V.sub.rms        9.11   6.80                                                  ______________________________________                                    

As shown in Table 1, the maximum voltage of the voltage V_(LC) applyingto liquid crystal is 9.11 V which is equal to the voltage obtaining thelight state V_(ON), and the minimum voltage is 6.80 V which is equal tothe voltage obtaining the dark state V_(OFF). It can be realized thatthe maximum value and the minimum value in the brightness curve in FIG.33 is obtained, a sufficiently high contrast ratio of 80 being obtained.And further the maximum amplitude in the signal voltage waveform can belowered up to V_(DP-P) =V_(DH) -V_(DL) =2.9 V.

Therein, in such a scanning voltage waveform as that in the embodiment,the higher voltage between the selective voltage V_(GH) and thenon-selective voltage V_(GLH) of the scanning signal voltage has to beset so as to satisfy the following equation.

    V.sub.GH ≧V.sub.DH +V.sub.TH +V.sub.M               (4)

    V.sub.GLH ≦V.sub.S1 +V.sub.TH -V.sub.M.             (5)

Therein, V_(S1) is the voltage indicated in FIG. 7 (e), V_(S1) =V_(DL)-ΔV_(GS)(-) -V_(B)(-). V_(TH) is the threshold value of the TFT, V_(M)being the margin voltage to ensure the ON/OFF operation of the TFT. Inthe embodiment, the above voltages are set as V_(TH) =0 V, V_(M) =4 V.And in order to eliminate the direct current component, the counterelectrode voltage V_(C) is set lower than the center voltageV_(D-CENTER) by ΔV_(C) =0.5 V.

Further, the scanning voltage V_(G)(i) is started up to the ON voltageV_(GH) with a time difference t_(d1) after the timing of the transitionof the scanning voltage V_(G)(i-1) in the precedent row from the ONvoltage V_(GH) to the non-selective voltage V_(GLH) or V_(GLL), and isfallen to the non-selective voltage V_(GLH) or V_(GLL) for the scanningvoltage V_(G)(i) with a time difference t_(d2) after the timing of thetransition of the scanning voltage V_(G)(i-1) in the precedent row fromthe ON voltage V_(GH) to the non-selective voltage V_(GLH) or V_(GLL).this is because of taking the deformation in the voltage waveform intoaccount, both the t_(d1) and t_(d2) in the embodiment are set 3 μs.(However, in a case, as in the embodiment, where a storage capacitance16 is connected to the scanning electrode in the precedent row andscanning is performed in the descending order of row, or where a storagecapacitance 16 is connected to the scanning electrode in the followingrow and scanning is performed in the ascending order of row, the t_(d1)and t_(d2) are not always required. In a case where a storagecapacitance 16 is connected to the scanning electrode in the precedentrow and scanning is performed in the ascending order of row, or where astorage capacitance 16 is connected to the scanning electrode in thefollowing row and scanning is performed in the descending order of row,the t_(d1) and t_(d2) are always required.)

In the embodiment as described above, although the liquid crystalcapacitance is very small as 33 fF and the storage capacitance is smallas 200 fF, the bias voltage of approximately 8 V can be appliedcomparing to the modulating voltage of 9 V (ΔV_(G) =V_(GLH) -V_(GL)-V_(GLLH) -V_(GL)). Therewith, the display system can be driven by avery low drive voltage in which V_(DP-P) (refer to FIG. 7 (c)) is only2.9 V. Therefore, the power dissipation in the signal driver 19, whichrequires electric power most, is decreased, which leads to decreasing inthe total power dissipation of the display system. Further, since thechip size in the signal driver can be decreased, the frame region arounddisplay panel can be decreased, which leads to realizing small sizedisplay system. Furthermore, since the percentage occupied by thedisplay area is increased, the performance in visibility can beimproved. Concurrently, since the storage capacitance are small andconsequently the opening area loss owing to the storage capacitance issmall enough to get a high opening ratio of 53%, the brightness of thedisplay screen can be improved.

The capacitance C_(G) per one scanning bus line is expressed by thefollowing equation.

    C.sub.G =M·{C.sub.S (C.sub.GS +C.sub.LC)+C.sub.GS (C.sub.S +C.sub.LC)}/(C.sub.S +C.sub.GS +C.sub.LC),                (6)

where M is the total number of pixels in the horizontal direction. Sincethe liquid crystal capacitance in the vertical electric field type islarge, C_(GS) <<C_(LC). Therefore,

    C.sub.G =C.sub.S ·C.sub.LC /(C.sub.S +C.sub.LC).  (7)

Supposing the bias voltage having magnitude of 80% of the modulatingvoltage ΔV_(GL), C_(S) =4C_(LC) is obtained and the minimum value ofC_(G) is (4/5)·C_(LC). On the other hand, in the parallel electric fieldtype, since C_(GS) =C_(LC) <<C_(S),

    C.sub.S =2C.sub.GS +C.sub.LC.                              (8)

When C_(GS) =C_(LC), C_(GS) =3C_(LC). As described above, since theliquid crystal capacitance C_(LC) in the parallel electric field type isapproximately one-tenth as small as that in the vertical electric fieldtype, C_(G) in the parallel electric field type becomes approximately0.4 times as small as C_(G) in the parallel electric field type.Generally, the cross-talk (horizontal smear), in which horizontallydrawn lines appear, takes place with change in the voltage waveformdeformation due to different image. Especially, in the driving methodwhere the voltage in the scanning electrode is modulated to decrease theamplitude of the signal voltage, the change in the voltage waveformdeformation in the scanning electrode effectively changes the effectivebias voltage. Therefore, by means of combining the driving method, wherethe voltage in the scanning electrode is modulated to decrease theamplitude of the signal voltage, with the parallel electric field type,the bias voltage can be sufficiently applied and the horizontal smearcan be suppressed.

In the embodiment, the capacitance per one scanning electrode is a smallvalue of 69 fF. Under this condition, the result of observing thescanning voltage waveform is that the waveform deformation in themodulating voltage hardly exists and the occurrence of horizontal smearcannot be confirmed visually. As described above, in the embodiment, thecompatibility of low drive voltage, high opening ratio and high imagequality can be attained. In addition to this, in the embodiment, sincethe difference between the voltage for displaying light state V_(ON) andthe voltage for displaying dark state V_(OFF) is lower than 5 V, the LSIhaving a absolute maximum supply voltage of lower than 5 V fabricatedwith a process for general purpose LSI (for example C-MOS level) can beused in the signal driver 19, which leads to improving the productivityof display system and decreasing the manufacturing cost.

When the modulating voltage is not superposed, that is, V_(GLH) =V_(GLL)=V_(GL), V_(DP-P) =18.2 V is obtained supposing V_(DH) =22.5 V, V_(DL)=4.3 V. Since V_(DP-P) =2.9 V in the embodiment, the V_(DP-P) can bedeceased below 1/6 as small as in the case of not superposing themodulating voltage.

Embodiment 2!

In this embodiment, driving waveforms are different from that inEmbodiment 1.

FIG. 8 shows driving waveforms in the embodiment. Although themodulating voltage ΔV_(GL)(+), ΔV_(GL)(-) applied in an identical framehas the same polarity of positive or negative in the all scanning linesin Embodiment 1, in the embodiment the polarity of the modulatingvoltage is reversing between the adjacent scanning lines in each other.Therefore, the polarity of the voltage V_(S) applied to the pixelelectrode is reversed in alternate order by every row, which isso-called the gate line inversion driving method. In the embodiment, theequations corresponding to (Equation 4) and (Equation 5) for Embodiment1 are given as follows.

    V.sub.GH ≧V.sub.DH +V.sub.TH +V.sub.M,              (9)

    V.sub.GL ≦V.sub.S1 +V.sub.TH -V.sub.M,              (10)

    V.sub.GLH ≦V.sub.S2 +V.sub.TH -V.sub.M,             (11)

where V_(S2) is the voltage value shown in FIG. 8, and V_(S2) =V_(DL)-ΔV_(GS)(+). When the voltage is set as V_(M) =4 V, the result is thatV_(D-CENTER) =15.0 V, V_(GH) =20.5 V, V_(GL) =0, V_(DH) =16.5 V, V_(DL)=13.6 V, V_(GLH) =9.0 V, V_(GLL) =9.0 V, V_(C) =14.5 V. And the voltageshift due to the parasitic capacitance C_(GS) between the gate electrodeand the source electrode ΔV_(GS)(+), ΔV_(GS)(-), ΔV_(B), the biasvoltage V_(B), the root-mean-square value V_(rms) of the voltage V_(LC)applying to liquid crystal are as shown in Table 2.

                  TABLE 2                                                         ______________________________________                                        Various Kinds of Voltage Values                                               Display                                                                       state            Light  Dark                                                  ______________________________________                                        ΔV.sub.GS(+)                                                                             0.31   0.45                                                  ΔV.sub.GS(-)                                                                             0.69   0.64                                                  V.sub.B(+)       7.61   8.31                                                  V.sub.B(-)       7.61   8.31                                                  ΔV.sub.B(-)                                                                              0.14   0.15                                                  ΔV.sub.B(+)                                                                              0.14   0.15                                                  V.sub.rms        9.11   6.80                                                  ______________________________________                                    

By means of employing the gate line inversion driving method in theembodiment, the maximum amplitude in the voltage of the scanningelectrode can be decreased from 28.6 V to 20.5 V although the marginvoltage V_(M) is set at the same value. Therewith, the absolute maximumsupply voltage and power dissipation of the scanning driver IC 18 can bedecreased.

As described above, in the embodiment, in addition to the same effectsas in Embodiment 1, a scanning driver IC having a low absolute maximumsupply voltage may be utilized and the power dissipation can be furtherdecreased.

Embodiment 3!

This embodiment is different from Embodiment 1 in the structure ofelectrodes and the method of driving.

FIG. 9 shows the plane structure of a region covering plural pixels on alower substrate. FIG. 10 is an enlarged view showing a part of thepixel. FIG. 11 is a cross-sectional view being taken on the plane of theline 11--11 in FIG. 10. FIG. 12 shows the circuit diagram of a displaysystem in accordance with the present invention.

As shown in FIG. 9 and FIG. 12, the trunks of the counter electrodes 4are formed in parallel to the scanning electrode 1 and are led to theedge of the panel in the opposite side of the scanning driver 18, thetrunks are connected together to connect to the counter driver 20. Thebranches are extended upward and downward from each of the trunks of thecounter electrodes. In order to realize a high opening ratio as high aspossible, one trunk of the counter electrode is formed for twovertically adjacent alignment of the pixels to decrease the number ofthe counter electrode interconnections to a half. The scanning electrode1 and the counter electrode 4 are formed by using the same metallicmaterial.

As shown in FIG. 11, a storage capacitance 16 is formed by sandwiching agate insulator 9 with the pixel electrode and the counter electrode 9.Since the counter electrode 4 is formed on another layer different fromthe pixel electrode 3 and the signal electrode 2 through the gateinsulator 9, the short circuit between the counter electrode 4 and thesignal electrode 2 is hardly occurred and the distance between the bothcan be made as short as approximately 3 μm. Therewith, since the area ofthe region not serving display between the signal electrode 2 and theadjacent counter electrode can be decreased, a high opening ratio equalto Embodiment 1 can be kept although the gap width between theelectrodes is decreased comparing to Embodiment 1 by dividing the pixelinto four parts (in Embodiment 1, dividing it into three parts) with thepixel electrode 3 and the branch portion of the counter electrode 4. Bydecreasing the gap between the electrodes, the voltage applied betweenthe electrodes can be decreased to apply the same magnitude of theelectric field to the liquid crystal. As described above, in theembodiment, the drive voltage can be decreased comparing to Embodiment 1with keeping the same brightness as that in Embodiment 1.

Since the most part of the electric field from the signal electrode 2terminates at the counter electrode 4 by forming the counter electrode 4immediately adjacent to the signal electrode 2, the capacitive couplingbetween the signal electrode 2 and the pixel electrode 3 can beprevented with shielding effect of the counter electrode, and thevoltage fluctuation in the pixel electrode due to the voltagefluctuation in the signal electrode can be suppressed. Therewith, thecross-talk in the vertical direction (vertical smear) can be suppressed,which improves the display quality. In the embodiment, the number of thesignal electrodes is 640×3, the number of the scanning electrodes being480, the number of the counter electrode interconnection being 240, thetotal number of the pixels being approximately one million equal to thatin Embodiment 1. Since the number of the counter electrodeinterconnections in the embodiment can be substantially decreasedcomparing to Embodiment 1, the probability of owing to break ininterconnection and the probability of failure short circuit betweeninterconnections are drastically decreased and the production yield ofthe panel can be improved. Although the trunk portion of the counterelectrode in the embodiment is commonly used for the two verticallyadjacent alignment of pixels, it does not essentially change the effectof the present invention and is in the scope of the present invention ifone trunk of the counter electrode is formed for each of the verticalalignment of the pixels.

FIG. 13 shows the driving waveform in the display system in theembodiment. The non-selective voltage of the scanning signal V_(G)(i-1),V_(G)(i) is changed in alternate order every scanning cycle betweenV_(GLH) and V_(GLL), and in synchronizing with this the voltage V_(C) inthe counter electrode 4 is also changed between V_(CH) and V_(CL).Therein, the amplitude of the OFF voltage |V_(GLH) -V_(GLL) | and theamplitude of the counter electrode voltage |V_(CH) -V_(CL) | are set inthe same value so that the relationship in the relative voltages amongthe pixel electrode 3, the scanning electrodes 1 and 13, the counterelectrode 4 becomes constant. By means of modulating the voltage V_(C)in the counter electrode at the same time, the modulation phase in thenon-selective voltage of the scanning signal can be brought to the samephase in all of the rows. Therewith, although the output of the scanningdriver IC in Embodiment 1 needs four kinds of voltage values, in theembodiment the circuit size inside the scanning driver IC can bedecreased since the display system can be driven with three kinds ofvoltage value. Further, if the modulating voltage is applied to theground voltage in the scanning driver IC or the OFF voltage throughoutput is used for the scanning side drive IC, the scanning side driveIC having binary output can be utilized and the display system can bemade further small.

As described above, in the embodiment, in addition to the same effectsas in Embodiment 1, the drive voltage can be further decreased and theoccurrence of cross-talk can be suppressed. And the production yield ofpanel can be improved. Further, since the scanning side drive IC can bemade small, the whole size of the display system can be made small.

Since the diving method in the embodiment can be applied to the pixelstructure in Embodiment 1, the scanning side drive IC in Embodiment 1can be also made small.

Although in the embodiment the modulating voltage is changed inalternate order by every one scanning cycle, it is possible to attainthe same effect if the modulating voltage is changed in alternate orderby every two scanning cycles or by every one frame cycle.

Embodiment 4!

FIG. 14 shows the structure of a region covering plural pixels in aliquid crystal display system in the embodiment. FIG. 15 is an enlargedview showing a part of the pixel.

In the embodiment, the counter electrode 4 is not provided, and thescanning electrode 13 in the precedent row is utilized as a counterelectrode facing against the pixel electrode 3. The orientation ofliquid crystal molecules in the liquid crystal layer is mainlycontrolled by the electric field E between the pixel electrode 3 and thebranch electrode extended from and perpendicular to the scanningelectrode 13 in the precedent row. Although in the embodiment the branchelectrode is led from the scanning electrode in the precedent row, thebranch electrode may be led from the scanning electrode in the followingrow. The storage capacitance 16 is formed in the structure bysandwiching the gate insulator 9 with the pixel electrode 3 and thescanning electrode 13 in the precedent row. Since the scanning electrode13 in the precedent row is placed on another layer different from thesignal electrode 2 through the insulator, the distance between thescanning electrode 5 and the signal electrode 2 can be decreased to 3μm. Further, since the counter electrode is not provided, the regionoccupied by the counter electrode wiring portion in the foregoingembodiments can be utilized for the opening portion. As described above,since the area of the region incapable of controlling light transmittingstate is decreased, a high opening ratio exceeding those in Embodiment 1and Embodiment 3 can be obtained although the gap between the electrodesis decreased by dividing the pixel into four parts. Therefore, in theembodiment, the brightness is further improved, the drive voltage beingdecreased comparing to Embodiment 1. By means of forming the branchelectrode of the scanning electrode 13 in the precedent row adjacent tothe signal electrode 2, most of the electric field from the signalelectrode 2 terminates at the branch electrode of the scanning electrode13. Therefore, the voltage fluctuation in the pixel electrode due to thevoltage fluctuation in the signal electrode can be suppressed, and thecross-talk in the vertical direction can be suppressed.

FIG. 16 shows the circuit diagram of the display system in theembodiment. Since the counter electrode is not provided, the counterdriver is not necessary. Since the counter electrode wiring and thecounter driver can be eliminated, the productivity of the panel can beimproved.

FIG. 17 shows the drive waveform in the embodiment. (a) and (b) show thescanning signal voltage, (c) showing the signal voltage, (d) showing thevoltage applied to the pixel electrode, (e) showing the voltagedifference between the pixel electrode and the scanning electrode. Inthe embodiment, the scanning signal is the same as in Embodiment 3.Since the modulating voltage in the scanning signal voltage applied tothe scanning electrode 1 and the modulating voltage in the scanningsignal voltage applied to the scanning electrode 13 in the precedent roware the same waveform, the displacement of the phase in the modulatingvoltage waveform due to the difference in the voltage waveforms in thecounter electrode and scanning electrode is eliminated, the bias voltagecan serve as the voltage applied to the liquid crystal withhigh-fidelity.

Putting the maximum gate voltage applied during non-selective period asV', V'=V_(ON) as shown in FIG. 17. In the embodiment, since thealternating current waveform is applied to the voltage applied to liquidcrystal, the threshold voltage V_(TH) of the TFT is controlled such asto satisfy V_(TH) >V_(ON). Therewith, the pixel electrode can operate tokeep the voltage even when the voltage applied to liquid crystal(-V_(ON)) having a negative value based on the non-selective voltage ofthe scanning signal is charged. In the embodiment, the gate thresholdvoltage V_(TH) is controlled with shifting toward high voltage side bymeans of make the amorphous silicon film thickness thin. The gatethreshold voltage V_(TH) is with in the range of V_(TH) <V_(G) <V_(D)+V_(TH), and the gate threshold voltage is defined by the gate voltageV_(G) at the intersecting point of the gate voltage V_(G) axis and astraight line which is obtained by plotting the root of drain currents√I_(D) against the gate voltage V_(G) and approximating the plots by astraight line. Although in the embodiment the gate threshold voltage iscontrolled by thinning the semiconductor film, there are other methodsfor controlling the gate threshold voltage by utilizing selection ofmaterial such as gate electrode material, gate insulator, semiconductorfilm; doping; back channel control and so on. Any one of the abovemethod or combination of the above may be employed, and these are withinthe scope of the present invention as far as it satisfies the conditionon the gate threshold voltage.

As described above, in addition to the effects in Embodiments 1 and 3,the embodiment has the effects in that the brightness is furtherimproved, the mass productivity of panel being improved.

Especially, by means of making V_(TH) exceed V_(ON), it becomes possibleto charge and keep the voltage being negative based on the non-selectivevoltage of the scanning signal, and consequently the liquid crystal canbe driven with alternating current. Therefore, it is realized to obtainan active matrix type liquid crystal display system having a long usefulservice life and a high image quality without occurrence of after-image.

The drive methods in Embodiments 1 and 2 may be applied to the pixelstructure in the embodiment.

Embodiment 5!

This embodiment is different from Embodiment 4 in drive method.

FIG. 18 shows the drive waveform in the embodiment. In the embodiment,the scanning electrode receives the scanning signal voltage in which thenon-selective voltage in the same frame is constant but thenon-selective voltage value is changed every frame, and the phasedifference by row is {1+(one scanning cycle)/(one frame cycle)}. Theimage signal voltage V_(D) is applied to the pixel electrode duringselective period through the TFT be means of applying the voltage to thesignal electrode in such a manner that the negative voltage is appliedto the signal electrode 2 when the non-selective voltage applied to thescanning electrode 13 in the precedent row is V_(GLH) which is thehigher voltage between the two non-selective voltages V_(GLH), V_(GLL),and a positive voltage is applied to the signal electrode 2 when thenon-selective voltage applied to the scanning electrode 13 in theprecedent row is V_(GLL) which is the lower voltage between the twonon-selective voltages V_(GLH), V_(GLL). Therewith, the alternatingcurrent drive waveform can be applied to the liquid crystal.

In the embodiment, since V'=V_(ON) as shown in FIG. 18, the thresholdvoltage of the TFT to satisfy V_(TH) >V_(ON) is required. It is realizedthat the polarity can be reversed every row with low electric powerconsumption without changing the non-selective voltage every scanningcycle as in Embodiment 4, and the flickering can be suppressed. In theembodiment, by means of putting the difference V_(GLH) -V_(GLL) betweenthe higher voltage of the non-selective voltage V_(GLH) and the lowervoltage of the non-selective voltage V_(GLL) equal to V_(ON) +V_(OFF)the maximum amplitude in the image signal voltage V_(PP-P) can belimited to V_(ON) -V_(OFF) and a low threshold voltage equivalent toEmbodiment 4 can be realized.

As described above, in the embodiment, the electric power consumption ofthe scanning driver can be decreased comparing to Embodiment 4.

Embodiment 6!

FIG. 19 shows the drive waveform in the liquid crystal display system inthis embodiment. Although the drive waveform in the embodiment isbasically the same as that in Embodiment 5, the different point fromEmbodiment 5 is in that the difference V_(GLH) -V_(GLL) between thehigher voltage of the non-selective voltage V_(GLH) and the lowervoltage of the non-selective voltage V_(GLL) is put equal to (V_(ON)+V_(OFF))/2. Therewith, as shown in FIG. 19 (c), although the maximumamplitude in the image signal voltage V_(PP-P) becomes a higher voltageof (3V_(ON) -V_(OFF))/2, the threshold voltage of the TFT V_(TH) becomeslarger than V'=ΔV/2=(V_(ON) -V_(OFF))/2 and consequently the maximumnegative voltage (-V_(ON)) can be applied to the liquid crystal.Therewith, the TFT having a lower threshold voltage comparing toEmbodiments 4 and 5 can be utilized, and the maximum amplitude of theimage signal voltage can be lowered by (V_(ON) +V_(OFF))/2 comparing tothe maximum amplitude of V_(DP-P) =2V_(ON) in the case of single-valuenon-selective voltage. Further, in the embodiment, the value (V_(ON)-V_(OFF)) can be made smaller by means of making the angle φ_(LC)larger, and the TFT having a further low threshold voltage can beutilized and concurrently the image signal voltage can be lowered.

As described above, in the embodiment, there is an effect in that theTFT having lower threshold voltage can be utilized comparing toEmbodiments 4 and 5.

Embodiment 7!

FIG. 20 shows the driving waveform in the liquid crystal display systemin this embodiment. In the embodiment, p-type TFT's and n-type TFT's arealternatively placed by row. Therewith, the TFT having a negativethreshold voltage V_(TH) can be used. For using the TFT having anegative threshold voltage V_(TH), it is necessary that the center valueV_(GL-P) of the non-selective voltage in the scanning electrode havingthe p-type TFT is higher than the center value V_(GL-N) of thenon-selective voltage in the scanning electrode having the n-type TFT,and at the same time the voltage difference exceeds V_(ON) +ΔV_(S).There, ΔV_(S) is the maximum value of feedthrough voltage. Therewith,the maximum amplitude V_(DP-P) of the image signal voltage can bedecreased up to V_(ON) +ΔV_(S) +ΔV.

As described above, in the embodiment comparing to Embodiment 4, the TFThaving a negative threshold voltage V_(TH) can be used and the imagesignal voltage can be lowered.

Embodiment 8!

This embodiment is different from Embodiment 1 in the structure of pixeland the driving method.

In the embodiment, the pixel is constructed as shown in FIG. 21. Theequivalent circuit of the pixel is as shown in FIG. 22. Thecross-sectional view being taken on the line E-E' in FIG. 22 is shown inFIG. 23. The cross-sectional view being taken on the line F-F' in FIG.22 is shown in FIG. 24. The cross-sectional view being taken on the lineG-G' in FIG. 22 is shown in FIG. 25. As shown in FIG. 21, thin filmtransistor elements 15a and 15b are formed in the pixel. As shown inFIG. 21, the signal voltage corresponding to an image is applied to adrain electrode 25a in the thin film transistor element 15a, andtransmitted to the pixel electrode 3 through a source electrode 26a anda through hole 31. The voltage in a counter electrode 4 for giving avoltage difference is applied to the pixel electrode 3 from the scanningelectrode 13a in the following row through a through hole 32, a drainelectrode 25b of the thin film transistor element 15b, and a sourceelectrode 26b. As shown in FIG. 25, a storage capacitance element 16a isformed with the pixel electrode 3, the counter electrode 4 and a gateinsulator 9. There, the storage capacitance element 16a is provided tokeep the voltage in the pixel electrode at a constant voltage byabsorbing the noise due to the signal. As described above, two thin filmtransistor elements are provided in a single pixel so that, as shown inFIG. 24, the direction of the electric field E between the pixelelectrode 3 and the counter electrode 4 mainly has the parallel orhorizontal component. Although two thin film transistor elements areused there, three or more thin film transistor elements may be used forredundant structure. Similarly, two or more storage capacitance elements16a may be used. Here, since the alignment between the pixel electrode 3and the counter electrode 4 is performed only by using a photo-mask, thedeviation in the electric field applied to the liquid layer issuppressed small. Further, since both of the source electrodes areformed on the same layer, the deviation in the distance d between thepixel electrode 3 and the counter electrode 4 can be suppressed lessthan 5%.

The driving method will be described below. FIG. 27 shows the waveformof the voltage applied to each of the electrodes. Here is employed theline at a time method where signals are written row by row. The scanningvoltage form 40: V_(G)(i) is composed of the selective pulse 41:V_(GON)(i) for selecting TFT's in a row and turning them into ON-stateand counter electrode voltage pulse 51: V_(C)(i) for giving the voltageV_(C) to the counter electrode in the precedent row. The counterelectrode voltage pulse 52: V_(GC)(i+1) in the (i+1)-th row is appliednearly in synchronizing with the selective pulse 41: V_(GON)(i) for thescanning line in the i-th row. Therefore, when the selective pulse 41 isapplied to the scanning voltage waveform 40 for the line in the i-throw, the thin film transistor elements 15a and 15b are turned ON, thesignal voltage wave from 61: V_(D)(j) and the counter electrode voltagepulse 52: V_(GC)(i+1) in the (i+1)-th row are written in the storagecapacitance 16a and the liquid crystal 5a connecting to the signalelectrode 2 and the scanning electrode 13a through the thin filmtransistor elements 15a and 15b respectively. After completion of thewriting period (1H) for the row, the scanning voltage waveform 40:V_(G)(i) falls to the OFF level (non-selective voltage), the thin filmtransistor elements 15a and 15b turning into the OFF state, the writtenvoltage is being kept. However, actually, the feedthrough voltage 76, 77take place by the coupling noise due to the parasitic capacitances ofthe thin film transistor elements 5a and 5b, the written voltage isbeing kept at that voltage. Here, the voltage applied to the liquidcrystal is the voltage 78 between the source voltages 71 and 72 in thethin film transistor elements 15a and 15b respectively. The brightnessof the pixel (transmission ratio) is determined by the voltage 78.

In the embodiment, the counter electrode inter connections for applyingvoltage to the counter electrode is not required by means of giving thevoltage from the scanning electrode in the following row to the counterelectrode. Different from Embodiments 4, 5 and 6, the TFT does notrequire a high threshold voltage, the TFT having the threshold voltageof nearly zero or lower than zero can drive the liquid crystal withalternating current. In a conventional driving method, the directcurrent component in the voltage applied to liquid crystal is generatedby the feedthrough voltage 76, 77 through the parasitic capacitances ofthe thin film transistor elements when the thin film transistor elementsare turned from ON state to OFF state. In the embodiment, the directcurrent component in the voltage applied to liquid crystal is notgenerated since it is canceled by the two thin film transistor elements.Therefore, although in a conventional system the direct currentcomponent is corrected in a counter electrode voltage, no correction isrequired in the embodiment. And since the liquid crystal can be drivenwith alternating current, no flickering occurs. Similarly, theimage-sticking due to direct current component is not recognized, thebrightness gradation is not apparently observed. Further, in a case ofemploying two-terminal element such as MIM diode, the image degradationsuch as non-uniformity of brightness due to the deviation in thethreshold of element being eliminated since the deviation is cancelledby two elements.

Embodiment 9!

The structure of this embodiment is the same as that in Embodiment 8except the following items. FIG. 28 is a plane view showing a pixel inthe embodiment, FIG. 29 being a diagram showing the equivalent circuit.The drain electrode in the thin film transistor element 15b givingvoltage to the counter electrode 4 is connected to the scanningelectrode 4 in the following row through a capacitance element 101. Thecapacitance element 6 for removing the noise due to signal connectedbetween the pixel electrode 3 and the counter electrode 4 is composed oftwo capacitance elements 6a and 6b. By this structure, all the throughholes required in Embodiment 8 can be eliminated. Therewith, thefabrication process such as patterning or holing on the insulatorbetween layers in the pixel requiring fine patterning becomesunnecessary, the short circuit or the connection defect between thedifferent layers due to the fault caused in an insulator fabricationprocess being eliminated. Furthermore, it can be realized to obtain ahigh quality liquid crystal display system by improving the openingratio with decreasing the through hole region unrelated to display.

In a case of giving a voltage to the counter electrode 4 throughcapacitive coupling, as shown in FIG. 29, the voltage in the counterelectrode 4 is determined by the ratio of the capacitance element 101 tothe composite capacitance of the storage capacitance s 16b and 16c.There, the voltage in the pixel electrode 3 is put as V_(ds), thevoltage in the scanning electrode in the following row as V_(GC)(i), thevoltage in the counter electrode 4 as V_(C)(i), the capacitances of theliquid crystal and the storage capacitance s 16b and 16c as C₁₇, C_(6a),C_(6b) respectively, the composite capacitance of these capacitance asC₁₀₂, and the capacitance of the capacitance element 101 as C₁₀₁. Sincethe liquid crystal capacitance between the pixel electrode 3 and thecounter electrode 4 is very small, the following relation can beobtained. ##EQU1## The voltage applied to the liquid crystal is asfollows. ##EQU2##

Therefore, if the capacitance C₁₀₁ of the capacitance element 101 issufficiently larger than the composite capacitance C₁₀₂, the capacitanceelement 101 can apply the voltage sufficient enough to drive the liquidcrystal. Even if the capacitance C₁₀₁ of the capacitance element 101 is2 to 3 times as large as the composite capacitance C₁₀₂, the displaycharacteristic is not affected only except the voltage amplitude in thescanning electrode in the following row becomes larger by 25% to 33%.

According to the embodiment, since the voltage in the counter electrodeis given through capacitive coupling, the fabrication process such aspatterning or holing on the insulator between layers becomesunnecessary, the opening ratio being improved with decreasing thethrough hole region unrelated to display. Furthermore, it can berealized to obtain a high quality liquid crystal display system in whichhas little faults due to the defects caused in the insulator fabricationprocess.

Embodiment 10!

The structure of this embodiment is the same as that in Embodiment 8except the following items.

FIG. 30 shows the driving waveform. Although the structure of pixel andthe equivalent circuit are the same as those in FIG. 21 and FIG. 22, theembodiment is characterized by that the polarity of the counterelectrode voltage pulse 5: V_(GC)(i+1) in the scanning voltage waveform40: V_(GC)(i+1) is alternatively reversed by every row with the centerof V_(CC). Since the liquid crystal voltage is equal to the voltagedifference between the signal voltage 61 and the counter electrodevoltage pulse 52, the gate line inversion driving of liquid crystal withlow voltage can be realized by means of alternatively reversing thecounter electrode voltage pulse 52 in the scanning voltage waveform inthe row following to the selected row. By means of selecting theamplitudes of the counter electrode voltages 51 and 52 properly andsetting the signal voltage and the center value of the counter voltagenearly equal to each other, the amplitude of the signal voltage can beminimized.

In the embodiment, by means of selecting the drive conditions asdescribed above, it can be realized that the maximum amplitude of thevoltage in the signal driver is decreased and the flickering isdecreased by using the gate line inversion method.

Embodiment 11!

The structure of this embodiment is the same as that in Embodiment 10except the following items.

FIG. 31 is a plan view showing 2 rows by 2 columns of pixels in theembodiment, and FIG. 32 being a diagram showing the equivalent circuit,FIG. 33 showing the driving waveform. The whole display area isconstructed by repeating this configuration of pixels. Although thestructure of the pixel is the same as that in the first embodiment shownin FIG. 21, the characteristic feature of the embodiment is as follows.The counter electrode 4 receiving voltage from scanning electrode isalternatively connected by every column to the scanning electrode 1 or13a, and concerning the driving method, the two kind of the counterelectrode voltage are alternatively applied to the scanning electrode byevery column during the scanning period whereas in Embodiment 10 the twokind of the counter electrode voltage are alternatively applied to thescanning electrode by every row.

According to the embodiment, the polarity of voltage to charging in theliquid crystal can be alternatively reversed by every column, and it canbe further realized that the horizontal smear is prevented by means ofcharging the signal voltage having the reversed polarity on the scanningelectrode to cancel the cross-talk current, and at the same time thesignal voltage is lowered. Furthermore, by means of alternativelyreversing the polarity by every column, it can be also realized that thevertical smear is prevented and a high image quality and low voltagedrive.

Although the present invention has been described referring to anembodiment on a transmitting type liquid crystal display system, thepresent invention is also effective for a reflection type liquid crystaldisplay system. Concerning the thin film transistor, the structure(normal stagger structure, inverted stagger structure, coplanerstructure and so on) and the material are not limited to the aboveembodiment.

A part or the whole of peripheral circuits (signal driver, scanningdriver, counter driver circuit) may be directly attached to the surfaceof the substrate 7 composing the panel to form an IC chip. A part or thewhole of peripheral circuits may be formed in a unit on the surface ofthe substrate 7 using, for example, polysilicone. By doing so, there isan effect that the whole display system can be made smaller than that ina case of forming the peripheral circuits outside the display panel.

Various kinds of office automation machines or portable machines can beconstructed by combining the liquid crystal display system with anprocessor, a memory, an input unit, an output unit, a communication unitand so on.

According to the present invention, in the method of switching liquidcrystal by using the electric field in parallel to the interface ofsubstrate, the voltage in the signal electrode is lowered by means ofmodulating the voltage in the scanning electrode, and low drive voltageand high opening ratio in pixel are accomplished. Thus, it becomespossible to provide a thin film transistor type liquid crystal displaysystem being low power dissipation and bright and excellent invisibility. Concurrently, the cross-talk (horizontal smear), which hasbeen a problem the driving method modulating the voltage in scanningelectrode, can be suppressed, and it becomes possible to provide a thinfilm transistor liquid crystal display system having a high imagequality. Further, by means of controlling the threshold voltage of thethin film transistor element or constructing both the n-type thin filmtransistor element and the p-type thin film transistor element, thescanning electrode can also serve as a counter electrode interconnectionand can be driven with low voltage. Furthermore, by means of utilizingtwo thin film transistor elements in a pixel, the counter electrodevoltage can be supplied through the scanning electrode, and the drivevoltage can be lowered and the image quality can be improved.

We claim:
 1. An active matrix type liquid crystal display system havinga plurality of switching elements comprising:a pair of substrates;signal electrode lines and scanning electrode lines formed on one ofsaid pair of the substrates and crossing each other in a matrix form; aplurality of pixels formed by adjoining said signal electrode lines andsaid scanning electrode lines; and a liquid crystal layer interposedbetween said pair of the substrates; wherein each pixel of said pixelscomprises an electrode structure for generating an electric field havinga component substantially in parallel with one of said pair of saidsubstrates upon application of at least one predetermined voltagethereto, and a scanning signal having at least two kinds ofnon-selective voltage values is applied to said scanning electrodelines.
 2. An active matrix liquid crystal display system according toclaim 1, wherein the electrode structure for generating the electricfield having the component substantially in parallel with one of saidpair of substrates includes a pixel electrode and a counter electrodearranged on said one of said pair of substrates.
 3. An active matrixliquid crystal display system according to claim 1, wherein each pixelof said pixels comprises a storage capacitance which is larger than acapacitance between a pixel electrode and a counter electrode.
 4. Anactive matrix liquid crystal display system according to claim 1,wherein:at least two switching elements are formed in a pixel, a sourceelectrode or a drain electrode of a first switching element beingconnected to the signal electrode, a source electrode or a drainelectrode of a second switching element being connected to a scanningelectrode adjacent to the scanning electrode corresponding to the gateelectrodes of said first switching element and said second switchingelement.
 5. An active matrix liquid crystal display system according toclaim 4, wherein:said second switching element is connected to saidadjacent scanning electrode through a capacitive element.
 6. An activematrix liquid crystal display system having a plurality of switchingelements comprising:a pair of substrates; signal electrode lines andscanning electrode lines formed on one of said pair of the substratesand crossing each other in a matrix form; a plurality of pixels formedby adjoining said signal electrode lines and said scanning electrodelines; and a liquid crystal layer interposed between said pair of thesubstrates; wherein each pixel of said pixels comprises an electrodestructure for generating an electric field having a componentsubstantially in parallel with one of said pair of said substrates uponapplication of at least one predetermined voltage thereto, a scanningsignal having at least two kinds of non-selective voltage values isapplied to said scanning electrode line, and a common voltage having atleast two kinds of voltage values is applied to at least one counterelectrode.
 7. An active matrix liquid crystal display system accordingto claim 6, wherein each pixel of said pixels comprises a storagecapacitance which is larger than a capacitance between a pixel electrodeand an adjacent one of the at least one counter electrode.
 8. An activematrix liquid crystal display system having a plurality of switchingelements comprising:a pair of substrates; signal electrode lines andscanning electrode lines formed on one of said pair of the substratesand crossing each other in a matrix form; a plurality of pixels formedby adjoining said signal electrode lines and said scanning electrodelines; and a liquid crystal layer interposed between said pair of thesubstrates; wherein each pixel of said pixels comprises an electrodestructure for generating an electric field having a componentsubstantially in parallel with one of said pair of said substrates uponapplication of at least one predetermined voltage thereto, a counterelectrode connected to said scanning electrode line, and at least oneswitching element having a threshold voltage which is larger than zero,and a scanning signal having at least two kinds of non-selective voltagevalues is applied to said scanning electrode line.
 9. An active matrixliquid crystal display system according to claim 8, wherein saidswitching element has a threshold voltage V_(TH) which is greater than amaximum voltage V_(ON) applied between a pixel electrode and an adjacentcounter electrode.
 10. An active matrix liquid crystal display systemaccording to claim 8, wherein said switching element has a thresholdvoltage V_(TH) which is greater than half of a difference between amaximum voltage V_(ON) applied between a pixel electrode and an adjacentcounter electrode and a minimum voltage V_(OFF) applied between thepixel electrode and the adjacent counter electrode.
 11. An active matrixliquid crystal display system having a plurality of switching elementscomprising:a pair of substrates; signal electrode lines and scanningelectrode lines formed on one of said pair of the substrates andcrossing each other in a matrix form; a plurality of pixels formed byadjoining said signal electrode lines and said scanning electrode lines;and a liquid crystal layer interposed between said pair of thesubstrates; wherein each pixel of said pixels comprises an electrodestructure for generating an electric field having a componentsubstantially in parallel with one of said pair of said substrates uponapplication of at least one predetermined voltage thereto, a counterelectrode connected to said scanning electrode line, and a switchingelement corresponding to each of said scanning electrode lines beingconstructed so as to have p-type characteristics and n-typecharacteristics in alternating order by every row of said scanningelectrode lines, to each of said scanning electrode lines having p-typeswitching transistor elements, a scanning signal which has at least twokinds of non-selective values higher than a non-selective voltageapplied to said scanning electrode line having n-type switchingtransistor element being applied, and to each of said scanning electrodeline having n-type switching transistor elements, a scanning signalwhich has at least two kinds of non-selective values lower than anon-selective voltage applied to said scanning electrode line havingp-type switching transistor element being applied.
 12. An active matrixliquid crystal display system according to any one of claims 1, 6, 8 and11, wherein:a liquid crystal composition, a direction of rubbing, aconfiguration of a polarization plate, distances between the substrates,and a distance between a pixel electrode and counter electrode are setsuch that the difference between the voltage for obtaining a light stateand the voltage for obtaining a dark state becomes below 5 V.
 13. Anactive matrix liquid crystal display system having a plurality ofswitching elements comprising:a pair of substrates; signal electrodelines and scanning electrode lines formed on one of said pair of thesubstrates and crossing each other in a matrix form; a plurality ofpixels formed by adjoining said signal electrode lines and said scanningelectrode lines; and a liquid crystal layer interposed between said pairof the substrates; wherein a storage capacitance which is larger than acapacitance between a pixel electrode and a counter electrode isconstructed in said pixel, and a scanning signal having at least twokinds of non-selective voltage values is applied to each pixel of saidpixels for modulating a voltage of said pixel electrode.
 14. An activematrix liquid crystal display system according to claim 13, wherein avoltage of a pixel electrode is changed by means of changing saidnon-selective voltage applied to said scanning electrode line mainlythrough said storage capacitance between said scanning electrode lineand said pixel electrode.
 15. An active matrix liquid crystal displaysystem according to claim 13, wherein said non-selective voltages of allof said scanning electrode lines are changed with an identicalamplitude, an identical cycle and an identical phase.
 16. An activematrix type liquid crystal display system comprising a first substratehaving on one surface a plurality of scanning electrodes, a plurality ofsignal electrodes formed so as to intersect with said plural scanningelectrodes, a switching element formed in each of the intersectingportions of said plural scanning electrodes and said plural signalelectrodes having a threshold value V_(TH) for said switching elementwhich is larger than half of a difference between a maximum voltageV_(ON), between a pixel electrode and a counter electrode for obtaininglight state or dark state, and a minimum voltage V_(OFF), between thepixel electrode and the counter electrode for obtaining light state ordark state, the pixel electrode being connected to said switchingelement, the counter electrode formed adjacent to said pixel electrodeand connected to said scanning electrode; a second substrate spaced fromsaid first substrate; a liquid crystal composition interposed in a gapbetween said first substrate and said second substrate; a scanningdriver applying a scanning signal to each of said plural scanningelectrodes; a signal driver supplying an image signal to each of theplural signal electrodes; where voltage is applied between said pixelelectrode and said counter electrode to give an electric field having acomponent substantially in parallel to at least one of said first andsecond electrodes to said liquid crystal component and to producedisplay; wherein:a scanning signal, which has values of thenon-selective voltages in alternate order by every frame and being keptat a constant voltage during a non-selective period, is applied to thescanning electrode.
 17. An active matrix type liquid crystal displaysystem according to claim 16, wherein:a voltage difference between twokinds of non-selective voltage values is set equal to the sum of themaximum voltage V_(ON) between the pixel electrode and the counterelectrode for obtaining light state and dark state and the minimumvoltage V_(OFF) between the pixel electrode and the counter electrodefor obtaining light state or dark state.
 18. An active matrix typeliquid crystal display system according to claim 16, wherein:a voltagedifference between two kinds of non-selective voltage values is setequal to the half of the sum of the maximum voltage V_(ON) between thepixel electrode and the counter electrode for obtaining light state ordark state and the minimum voltage V_(OFF) between the pixel electrodeand the counter electrode for obtaining light state or dark state. 19.An active matrix type liquid crystal display system comprising a firstsubstrate having on one surface a plurality of scanning electrodes, aplurality of signal electrodes formed so as to intersect with saidplural scanning electrodes, a switching element formed in each of theintersecting portions of said plural scanning electrodes and said pluralsignal electrodes, a pixel electrode having p-type characteristic andn-type characteristic in alternate order by each row of the pluralscanning electrodes connected to said switching element, a counterelectrode formed adjacent to said pixel electrode; a second substratespaced from said first substrate; a liquid crystal compositioninterposed in a gap between said first substrate and said secondsubstrate; a scanning driver applying a scanning signal to each of saidplural scanning electrodes; a signal driver supplying an image signal toeach of the plural signal electrodes; where voltage is applied betweensaid pixel electrode and said counter electrode to give an electricfield having a component substantially in parallel to at least one ofsaid first and second substrates to said liquid crystal component and toproduce display; wherein:a voltage of a non-selective voltage in thescanning signal applied to the scanning electrode having a p-typeswitching transistor element is higher than a voltage of a non-selectivevoltage in the scanning signal applied to the scanning electrode havingan n-type switching transistor element, a voltage difference exceeding amaximum voltage V_(ON) between the pixel electrode and the counterelectrode for obtaining a light state or a dark state.
 20. An activematrix type liquid crystal display system comprising a first substratehaving on one surface a plurality of scanning electrodes, a plurality ofsignal electrodes formed so as to intersect with said plural scanningelectrodes, a first switching element, a second switching element havinga source electrode or drain electrode connected to one of said pluralscanning electrodes, a pixel electrode connected to one of said firstand second switching elements, a counter electrode formed adjacent tosaid pixel electrode; a second substrate spaced from said firstsubstrate; a liquid crystal composition interposed in a gap between saidfirst substrate and said second substrate; a scanning driver applying ascanning signal to each of said plural scanning electrode; a signaldriver supplying an image signal to each of the plural signalelectrodes; where voltage is applied between said pixel electrode andsaid counter electrode to give an electric field having a componentsubstantially in parallel to at least one of said first and secondsubstrates to said liquid crystal component and to produce display;wherein:the counter electrode voltage is supplied from said scanningelectrode.
 21. An active matrix type liquid crystal display systemaccording to claim 20, wherein:the counter electrode voltage suppliedfrom said scanning electrode changes according to a polarity of an imagesignal voltage.